The present invention relates to a new connecting structure and its connection method, and to a rotating electrical machinery having the above connecting structure and an alternating current generator using this rotating electrical machinery.
Conventionally, the connecting method for the cable having an insulated coating for the electrical machinery includes the insulated coating of the electric cable having the insulated coating is removed by a mechanical or chemical method, and the electric cable with its metallic surface being exposed is made wound around the electrically conductive member.
As for the connecting method for connecting directly the electric cable to the electrically conductive member without removing the insulated coating of the electric cable having the insulated coating, using a U-shaped electrically conductive member and inserting an electric cable having a insulated coating into the depression part of the U-Shaped electrically conductive member, and pressing the electric cable with the electrode for resistance welding and applying the electric current, then the electrically conductive member and the electrode generate heat. In this method, due to the generated heat, the insulated coating is made soften and flow out, and then the electric cable having the insulated coating and the electrically conductive member are connected. In addition, there is another prior known in Japanese Patent Laid-Open Number 2-137306 (1990). In this official information, what is disclosed is a method for connecting the coils with the heat at the connecting terminal developed by the heat generated by applying the electric current into the resistance. Those methods for connecting the cable is effective because the step for removing the coating can be omitted.
In the connecting method in which the coating is mechanically removed, however, it is difficult to remove the coating completely and constantly and the electric cable having the insulated coating may be damaged, which leads to the reduction in the cross-section of the electric cable and hence the reduction in the reliability for connecting strength. The chemical connecting method gives a great effect to safety and environmental issues, and the solder-based connecting method has such a problem that the mechanical strength is reduced in a high temperature, both of which leads to reduction in the reliability. In addition, in such a connecting method as the coating is not removed and the connecting support member is not used, only the electric cable and the electrically conductive member contact mechanically to each other but the metallic contact is not established. Though the electrical connectivity is guaranteed by caulking the electrically conductive member, there found such a problem in the electrical characteristic and the strength reliability because the caulking strength is reduced due to vibration or heat cycle.
In order to solve the above problems in the above official report, a connecting support member is installed in the connecting terminal formed in U-shape and the electric cable having the insulated coating is inserted and pressed and then the electric cable and the electrically conductive member are made connected to each other by the resistance heat generated at the connecting terminal with an electric current being applied.
However, as what is inserted in the terminal formed in U-shape or in a round form is the electric cable having the insulated coating, the applied electric current is concentrated at the bending or curvature part and thus there is such a problem that this part is overheated, melt down or buckled. In order to solve this problem, it is required to make the cross-section large enough to stay with the applied electric current, and consequently to make the size of the electrically conductive member large enough. Therefore, in the connecting method in which the electric cable having the insulated coating is connected to the electrically conductive member by using the conventional connecting support member, it is required to consider the shape and material of the electrically conductive member in compliance with the wire diameter of the electric cable having the insulated coating.